Introduce global "Filtered Actions" that are invoked when a filter evaluates to a non-empty result

[Jermolene]

This PR introduces a potentially highly dangerous new feature: the ability to execute action strings whenever a filter expression evaluates to a non-empty result.

A filtered action is a tiddler with the tag $:/tags/FilteredActions, and a filter field containing a filter expression. The actions are taken from the text field.

It is useful for automating actions. As an example, this PR amends the Tour plugin so that the user no longer needs to click the "next" button to advance to the next step.

To try a demo:

• Use the Tour in the preview of this PR
• Compare with the current prerelease of the tour

However, the danger is that it is very easy to set up a filtered action that is invoked continuously.

The system currently throttles filtered actions so that they occur no more often than every 500ms, which avoids the thrashing that would occur if the actions were allowed to occur as rapidly as possible.

I think the design may need to refined. For example, I wonder if the throttling should apply to individual filtered actions, rather than the whole set. It is also possible that we might avoid accidental thrashing if we only triggered a filter action the first time it returns a result, and ignore repeated results after the first one.

Progress

• Basic throttled operation
• Support providing variables to the filter expressions (needed by the step-success-filter-var feature of the Tour plugin)

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Name	Status	Preview	Updated (UTC)
tiddlywiki5	✅ Ready (Inspect)	Visit Preview	Feb 22, 2024 5:29pm

[pmario]

hmmm. I'm not sure what this filter does, so I doubt users will be able to create something like this.

[Jermolene]

I would agree that complex filters are complex, but I don't know how that relates to this PR.

[saqimtiaz]

While working with tm-http-request today I keep running into situations where this would be useful.

For example, a tiddler is meant to show data retrieved via a HTTP request. At present the best I can do is either ensure that the user navigates to this tiddler only via a button that triggers the request and the navigation simultaneously, or by adding a button along the lines of "click here to load the data" on the display tiddler, neither of which is palatable. So I am having to resort to using a modal so that I can control how the display of this part of this interface is initiated and also trigger the HTTP request.

It would be much more preferable to have the presence of the tiddler in the story river be the trigger for the HTTP request.

[Leilei332]

Would it be possible to trigger actions at a certain time (like what crontab does in Linux) based on this feature? I think this is useful for tiddlywiki to run automated tasks.